Proximity-responsive gas burner igniter



Nov. 11, 1969 ZIELINSKI ETTA!- 3,477,797

PROXIMITY-RESPONSIVE GAS BURNER IGNITER Filed Oct. 15, 1967 FICA.

INVENTORSZ ROBERT J. ZIELIINSKI DAViD P. MET ZGER -v-7'0 CIRCUIT ATTYS,

United States Patent Int. Cl. F2311 7/12 US. Cl. 431-256 3 ClaimsABSTRACT OF THE DISCLOSURE A system which responds to touching by anoperator to generate pulses, for example to generate ignitlon pulses forgas burners. An alternating voltage source, such as the'usual AC. powerline, having one output termlnal grounded is connected with itsungrounded upper terminal in series with a rectifier and a touch pointelectrode. A series combination of a resistor and a capacitor isconnected in parallel with the rectifier, and the glow lamp is connectedin parallel with the capacitor. When an operator who is electricallyconnected to ground, as by standing on a floor or on-the ground, touchesthe touch-point electrode, the circuit for the alternating voltagesource is completed so that a series of rectified voltage pulses isproduced across the rectifier. These successive voltage pulses cause thecapacitor to charge up incrementally to a level at which the normallynon-conductive glow lamp fires and discharges the capacitor. In this wayrepetitive current pulses are produced through the glow lamp at a ratelower' than the frequency of the alternating source. The pulses throughthe glow lamp may be used to operate a sparkigniter for a gas burner,and the touch point is preferably located on a manual gascontrol valvefor the burner, so that when an operator turns on the burner histouching of the valve control will generate the ignition sparks requiredto ignite the burner.

Background of the invention Thisinvention relates to apparatus forproducing electrical pulses in response to proximity of an object, andespecially to such apparatusifor the electrical ignition of a gas burnerin response to the touch of an operator.

There are various applications in which it is desirable to control orinitiate electrical action in response to proximity of an object,without requiring operation of a mechanical switch. Such apparatus iscommonly known as a touch control system, one form of which is commonlyused, for example, in connection with the floor-selection buttons inelevator cars While there are many applications for the subject of thepresent invention, it will be described primarily with reference toelectrical ignition systems for automatically igniting gas emanatingfrom gas burners. i

It is known that a gas burner may be ignited by sparks produced at sparkelectrodes adjacent the burner in response to pulses of current appliedto a spark transformer supplying the spark electrodes. The presentinvention in one form provides apparatus for producing ignition sparksin such a system in response'to touching of a touch point by anoperator.

It is therefore an object of the invention to provide new and usefulapparatus for producing electrical pulses in response to the proximityof an electrically-conductive object.

Another object is to provide such reliable in a wide range ofapplications;

A further object is to provide new and useful apparatus for producingsparks adjacent a gas burner in reapparatus which is 3,477,797 PatentedNov. 11, 1969 sponse to touching of a portion of the apparatus by anoperator.

A still further object is to provide a system including a gas burner anda manually-controllable valve for supplying gas to the burner, in whichelectrical ignition sparks are produced adjacent the burner to ignite itin response to touching of the control valve by the hand of an operator.

Summary of the invention These and other objects of the invention areachieved by the provision of a system comprising a source of varyingvoltage, electrode means, asymmetrically-conductive means connectedbetween said electrode means and one terminal of said source, a seriescombination of capacitive means and resistive means connected inparallel with said asymmetrically-conductive means, and voltagethreshold means in parallel with said capacitive means. The electrodemeans is normally effectively isolated electrically from the otherterminal of the voltage source so that charge does not build up on thecapacitive means and the voltage threshold means is not operated.However, When an electrically-conductive movable object, such as a humanbody, which is coupled to the other terminal of the source is broughtinto proximity to the electrode means so as to be only very closelyspaced from it or to touch it, rectified voltage pulses are producedacross the asymmetrically-conductive means which charge the capacitivemeans in successive increments until the voltage thereacross exceeds thethreshold voltage of the voltage threshold means thereby'discharged andthe cycle repeated. Accordingly, when the electrically-conductivemovable object is in proximity to the electrode means, repetitive pulsesof current are produced through the voltage threshold means, thesepulses terminating when the movable object is removed from proximity tothe electrode means.

in a preferred embodiment, the electrode means are located on one ormore manual controls for the valves supplying gas to one or more gasburners, and the current pulses through the voltage threshold means,.which may be an ordinary glow lamp, are used to produce sparks at sparkelectrodes adjacent the one or more burners. With this arrangement, anoperator manually operating one of the valves to turn on the gasthereby. causes ignition sparks to occur automatically at the burners,the sparks terminating when the operator removes his hand from thecontrol knob. 1

Because in the arrangement of the invention successive cycles of thealternating voltage have a cumulative effect in causing voltage acrossthe capacitor to approach the threshold level of the threshold means,repetitive pulses pulses are produced in the voltage threshold meansdespite substantial variation in the impedance of the movable object,and particularly despite relatively highimpedance values of the movableobject which tend to reduce the speed with which a capacitor can becharged through the movable object. In addition, the capability ofproducing pulses at a rate substantially lower than that of thealternating voltage source enhances'and simplifies the production ofsparks for ignition purposes; thus, in a preferred embodiment in whichthe sparks are produced by discharge of a capacitor, the larger timebetween successive pulses permits use of a larger discharge capacitorand thereby makes available larger discharge energies for operating thespark-generating equipment.

Brief description of the figures These and other objects and features ofthe invention will be more readily understood from a consideration ofthe following detailed description, taken in connection with theaccompanying drawings, in which:

FIGURE 1 is a schematic electrical diagram illustrating one embodimentof a circuit in accordance with the invention for producing pulses inresponse to proximity of an object to a touch point;

FIGURE 2 is an electrical schematic diagram illustrating a simplifiedequivalent-circuit diagram corresponding to the circuit of FIGURE 1;

FIGURE 3 is a schematic diagram illustrating an application of theinvention to automatic ignition of gas burners; and

FIGURE 4 is an elevational fragmentary view, partially in section,illustrating a touch-control valve knob arrangement suitable for use inthe system of FIGURE 1.

Description of preferred embodiments Referring now to the embodiment ofthe invention il lustrated in FIGURE 1, a source of varying voltage,which may be the usual 60-cycle power line, has its lower terminalgrounded and its upper terminal connected to the anode of a dioderectifier 12, the cathode of which is connected through a resistor 14and a capacitor 16 to a touch-point electrode 18. A series combinationcomprising resistor and a capacitor 22 is connected in parallel withrectifier 12 and resistor 14. A voltage threshold device 24, illustratedas a gaseous glow lamp, and a load resistor 26 are connected in serieswith each other and in parallel with capacitor 22. Anelectrically-conductive movable object 28 connected to ground at one endis movable into close proximity to touch-point electrode 18, preferablyinto direct contact therewith; the brokenline resistor and capacitorcombination 29 represent the equivalent impedance to ground produced bythe movable object 28. Object 28 may comprise the body of an operatorwhose feet are effectively connected to ground potential and whose handis movable into contact with touch-point electrode 18.

In the operation of the arrangement of FIGURE 1, touch-point electrode18 is normally effectively isolated from ground, there is therefore noreturn path for current from source 10, capacitor 22 remains dischargedand glow lamp 24 is non-conductive. However, when the upper end ofmovable object 28 touches touch-point electrode 18, e.g. when theoperator touches the latter electrode, a circuit is completed for source10 by Way of rectifier 12, resistor 14, capacitor 16, touch-pointelectrode 18 and the resistance and capacitance to ground of object 28.Under these conditions, rectifier 12 causes positive rectified half-wavepulses of voltage to appear at junction point 30 between resistor 14 andcapacitor 16, rectifier 12 serving in elfect as a clipper to remove thenegative half-cycles of the alternating voltage waveform. Resistor 20and capacitor 22 are sufficiently large that capacitor 22 responds tothe first rectified voltage pulse to charge only to a small fraction ofthe peak value thereof, but responds to succeeding rectified voltagepulses to charge progressively further in increments toward anequilibrium value approximately equal to the average value of thehalf-wave voltage pulses.

However, before this equilibrium value of voltage on capacitor 22 isreached, the voltage on capacitor 22 reaches a threshold level at whichglow lamp 24 fires and becomes highly conductive, and at this timecapacitor 22 is substantially discharged through glow lamp 24 and loadresistor 26. After such discharge, glow lamp 24 resumes itsnon-conductive state, the incremental charging of capacitor 22 beginsagain, and the cycle repeats itself. In this way repetitive pulses ofcurrent through, and voltage across, load resistor 26 are produced at arate which is a submultiple of the frequency of the alternating voltagesource 10, so long as touch-point electrode 18 is contacted by object28. When object 28 is removed from the vicinity of touch-point electrode18, charging of capacitor 22 ceases and pulses at load resistor 26 nolonger occur.

Resistor 14 and capacitor 16 are provided in the preferred embodimentmerely to minimize shock hazard. The basic operating elements of FIGURE1 may therefore be represented in simplified form as shown in theequivalent circuit of FIGURE 2, wherein corresponding parts areindicated by numerals corresponding to those of FIGURE 1 with the sufiixA added thereto, and wherein the block Z represents the combinedimpedances of the movable object (e.g. the body of the operator whentouching the touch point) and of the capacitor 16. The value of resistor14A is significantly lower than that of the impedance Z, so that most ofthe voltage of the half-wave pulses appears at junction point 30A. Thetime constant of resistor 20A and capacitor 22A is sufiiciently longcompared with the rectified voltage pulses that capacitor 22A is onlypartially charged in response to each rectified pulse, thereby producingthe desired incremental increase in charge in response to successiverectified pulses.

The voltage pulses across, and the current pulses through, resistor 26of FIGURE 1 may be used for any of a variety of purposes; and, in fact,where a visual or optical indication of touching is desired, the pulsesof light from glow lamp 24 may be used as the indications, in which caseresistor 26 may be short-circuited and eliminated. As will 'be describedwith reference to FIG- URE 3, the pulses of current through the glowlamp may advantageously be used to drive an ignition spark generatorcircuit for igniting a gas burner.

Referring now particularly to FIGURE 3, in which parts corresponding tothose of FIGURE -1 are indicated by corresponding numerals followed bythe sufiix B, the alternating voltage source 10B has its lower ouputterminal grounded and may be the usual public-service power generatorsupplying power lines 50' and 52, which terminate in an ordinaryhousehold electrical outlet socket 54. The remainder of the apparatus ofFIGURE 3 may comprise the surface burner unit of a domestic gas rangeand electrical ignition circuitry therefor mounted on an interior wallof the range cabinet and connected to electrical outlet 54 by means ofan appropriate plug 56.

More particularly, the usual four gas burners of a domestic rangerepresented as B B B and B are supplied with fuel gas from a common gasmanifold 60 by way of manually-operable gas valves V V V and Vrespectively; corresponding manual control knobs for the valves arerepresented, respectively, at 62, 64, 66 and 68. Each of the burners isprovided with a pair of spark electrodes such as 70, these pairsbeing'connected in series with each other and with the secondary 72 of aspark transformer 74 which generates pulses of voltage to operate all ofthe spark electrodes simultaneously. The function of the circuitry oftheinvention now to be described is therefore to produce such sparkignition pulses only when an operator touches one of the four manual gascontrol knobs 62,64, 66 and 68.

Referring now to the detailed structure of the electrical circuitry ofFIGURE 3, the two leads from the plug 56 are connected to opposite endsof the primary of an isolationtransformer 82 having a secondarywin'ding84. Such isolation transformers are commonly utilized for commercialapparatus to minimize shock hazard and to minimize the effects ofshort-circuits. However, an isolation transformer is not necessary inall applications, and when it is not utilized the input'leads totransformer primary 80 are directly connected to the "pair of outputleads from output transformersecondary 84 to provide the type ofconnection shown in FIGUREl.

Even though such an isolation transformer provides adequate isolationfor safety purposes, it has been found that there is generallysufiicient unbalanced coupling between prirnary and secondary thereof toprovide the required circuit action, provided that the polarity of thepair of leads to the primary and the'polarity of the pair of leads tothe secondary are appropriate. Thus in the embodiment of FIGURE 3 it isthe-output lead 86 of transformer secondary'84, connected'to the anodeof diode 12B and to the lower, negative plate of capacitor 22B, whichshould be the off-ground or hot side of the circuit. The parallelresistance and capacitance circuit 88 shown in broken line between thelower end of transformer primary 80 and transformer secondray 84represents such unbalanced coupling which, in effect, couples the hotside of the power line to line 86 as desired. Since there are only afour combinations of polarities for the primary and secondary windings'of transformer 82, a suitable combination may be readily determinedwhen the circuit is being constructed by trying the four diiferentcombinations,-'i.e. reversing the polarity of plug 56 and the polarityof the connections to the secondary 84 of the transformer. The result isthat, once the construction of the system has been completed, the line86 receives alternating voltage with respect to groundsirnilar to thatprovided by the ungrounded terminal of source in FIGURE 1, so long asthe plug 56 is inserted in the correct polarity.

The circuit elements 12B,"14B, 16B, 20B, 22B, 24B and 26B all act aspreviously describedwith reference to FIGURE 1, although the load for.the glow lamp 24B in this case includes the gate-to-cathode currentpath of a silicon controlled rectifier 90 and the touch-point electrodecomprises any one of the valve control knobs 62, 64, 66 or 68, thelatter knobshaving exposed conductive portions which are connected- 'inparallel and to the upper plate of capacitor 16B. v

One suitable construction for the touch-point control knobs is shown inFIGURE 4, in which parts corresponding to those of FIGURE 3: areindicatedby. corresponding numerals with the suflix C. Thus the gassupply manifold line 60C provides fuel gas to a gas valve such as V, forsupply through pipe 90 to burner B for example. The rotatable shaft 94for controlling valve V is fastened by an appropriate transverse pin 96to a sleeve portion 98 of the control knob 62C. The latter knob iscomposed primarily of an insulating material, such as plastic, but isprovided on the etxernal front portions thereof with anelectrically-conductive coating 102 of metal which extends over aperipheral region on the back side of the knob as at 104. The entireassembly is mounted by any suitable means (not shown) within the rangecabinet 106. An electrically-conductive sliding spring contact 108 ismounted on an insulating support block 110 on the interior of cabinet106 by an appropriate screw 112 so as to bear against, and provideelectrical contact to, the rearward portion 104 of metal coating 102 ascotnrol knob 62C is turned. A wire lead 114 is also connected to springcontact 108 and leads to the upper side of capacitor 16B in FIGURE 3. Asimilar arrangement is provided for all of the control knobs. Theconductive coating on any of the control knobs therefore serve as anactuating touch point for the system.

Returning now to FIGURE 3, the anode-cathode elements of siliconcontrolled rectifier (SCR) 90 are supplied with filtered direct voltageby connecting the cathode element thereof to line 86 and by connectingthe anode element thereof to the opposite or upper end of isolatingtransformer secondary 84 by way of spark transformer primary 120,resistor 122, and diode rectifier 124. A capacitor 126 connected inparallel with the series combination of spark transformer primary 120and SCR 90 serves as a discharge capacitor on which charge is storeduntil it is discharged abruptly through transformer primary 120 byconduction through SCR 90 produced in response to firing of glow lamp24B. Each such discharging of capacitor 126 through spark transformerprimary 120 produces a corresponding high voltage pulse across thesecondary 72 of the spark transformer, which is applied to the seriescombination of the burner spark electrodes 70. Resistor 127 in parallelwith capacitor 126 is not essential to operation, but serves to dampextreme transient voltages and to discharge capacitor 120 when thesystem is not plugged in.

In the operation of the arrangement shown in FIG- URES 3 and 4, with thesystem arranged as shown and all gas control valves in their OFFpositions, no gas emanates from any of the burners and no ignitionsparks are produced. However, as soon as an operator touches theconductive portion of one of the control knobs to turn on the gas to oneof the burners, this touching produces the previously-describedincremental buildup of charge on capacitor 22B in response to successiverectified voltage pulses at junction point 30B, until the voltage acrosscapacitor 22B reaches the firing voltage for glow lamp 24B. At thelatter time the glow lamp 24B fires, producing a pulse of currentthrough the gate electrode of silicon controlled rectifier and acorresponding pulse of current through spark transformer primary 120 ascapacitor 126 discharges through it. This pulse of current produces ahigh-voltage pulse across all of the burner spark electrodes in series,including the one then being supplied with gas. When the glow lamp 24Bhas discharged capacitor 22B, the voltage across the glow lamp 243 fallsbelow the extinction level thereof and the lamp becomes non-conductive.This permits capacitor 22B to recharge and also turns 01? siliconcontrolled rectifier 90 so that capacitor 126 is recharged by way ofrectifier 124. In this way repetitive high voltage ignition-pulses areapplied to all of the burner spark electrodes including the pairadjacent the burner from which gas is emanating so that the latterburner is ignited. The ignition sparks continue as long as the operatortouches the control knob, but as soon as his hand is removed the sparksterminate.

Without in any way thereby limiting the scope of the invention, thefollowing specific example of parameters, values and elements of atypical system in accordance with FIGURE 3 are given in the interest ofcomplete definiteness. Capacitor 126-4 microfarad electrolyticcapacitor, 250

volt D.C. rating Capacitor 22B-0.002 microfarad capacitor, 200 volt D.C.rating Capacitor 16B--0.001 microfarad capacitor, volt D.C. rating Diode124-400 volts peak inverse rating Diode rectifier 12B-200 volt peakinverse rating Glow lamp 24B-type NE-2 glow lamp, fires at 75 voltsResistor 1221,000 ohms, /a watt rating Resistor 127-15 megohms, /2 wattrating Resistor 20B22 megohms, /2 watt rating Resistor 14B1.5 megohms,watt rating Isolation transformer 821l5 volt A.C. isolation transformerwith H-type laminate iron core, primary and secondary wound one on topof the other. Spark transformer 74commercial spark transformer,

AMGLOW type MTSS Silicon controlled rectifier 90General Electric typeClO 6 B, 200 volt peak inverse rating Alternating voltage source10BStandard -volt power line source With this specific arrangement,three high volt-age spark pulses per second were produced, althoughwhere the operator is more than ordinarily insulated from ground byrubber shoe soles or the like the pulsing rate may be somewhat slower.

It will be noted that the external impedance between touch point andground is not as critical a factor as in a system in which a capacitormust be fully charged by each cycle of line voltage. lIn the latter typeof system a substantial increase above normal of the external impedancewill prevent the glow lamp from firing at all, whereas in the system ofthe present invention the effect of such increases in externalimpedances, over a substantial range, is merely to require more cyclesfor charging the capacitor 22B and hence a reduced output pulse rate.Also, because of the relatively low pulse rate there is more time forcapacitor 126 to charge between pulses, the capacitor can be made largerthan otherwise would be the case, and with a given pulse therefrom morepairs of spark electrodes more reliably operated.

As mentioned above, the system can be operated with or without theisolation transformer; also, capacitor 16B and resistors 30B and 26B canbe eliminated, the polarity of diode 128 can be reversed provided theSCR circuit is suitably modified, and other forms of voltage thresholddevice an of spark generating apparatus can be used in variousapplications.

Thus while the invention has been described with particular reference tospecific embodiments thereof in the interests of complete definiteness,it will be obvious to one skilled in the art that it may be embodied ina variety of forms diverse from those specifically described withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

We claim:

1. A touch-control system for igniting gas burners, comprising:

electrical ignition means disposed adjacent a gas burner and responsiveto voltage pulses applied thereto to produce a spark for igniting gasfrom said burner;

a source of alternating voltage, one output terminal of said sourcebeing grounded; manual control means for turning said burner on and off,said control means comprising electrode means positioned to beelectrically coupled to the hand of an operator manipulating saidcontrol means;

rectifying means connected between said electrode means and the otheroutput terminal of said source for producing rectified voltage pulsesacross said rectifying means when said operator touches said controlmeans;

a series combination of capacitive means and resistive means in parallelwith said rectifying means whereby said capacitive means is chargedincrementally to a predetermined level in response to a series of saidrectified voltage pulses;

voltage threshold means in parallel with said capacitive means andresponsive to the voltage across said capacitive means to becomestrongly conductive each time said last-named voltage reaches saidpredeter mined level, thereby repetitively to discharge said capacitivemeans and to produce repetitive pulses of current through said voltagethreshold means; and means responsive to said repetitive pulses ofcurrent for applying voltage pulses to said ignition means.

2. The system of claim 1, in which said voltage threshold meanscomprises a gaseous discharge device, and said means responsive to saidrepetitive pulses comprising a silicon controlled rectifier suppliedwith said repetitive pulses and a spark transformer operated by theoutput of said silicon controlled rectifier.

3. The system of claim 1, comprising an iron-core isolating transformerconnecting said other output terminal of said source to the side of saidrectifying means opposite that connected to said electrode means.

References Cited UNITED STATES PATENTS 3,200,305 8/1965 Atkins.

3,286,134 11/1966 Myers.

3,313,960 4/ 1967 Bory.

3,377,125 4/1968 Zielinski 431-74 OTHER REFERENCES General Electric SCRManual, 3rd edition, pp. 121 and 122.

FREDERICK L. MATTESON, JR., Primary Examiner H. B. RAMEY, AssistantExaminer U.S. Cl. X.R. 340-25 8 3,477,797 Dated November 11, 1969 PatentNo.

Inventor) Robert J. Zielinski and David P. Metzger It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

line 31 after "means" insert and the voltage threshold means therebybecomes strongly conductive The capacitive means is Column 2,

Column 7 line 13 for "an" read and SGNED AND SEALED JUL211970 Amen M'mmh7711mm 3. Wm. Ed at I: Comissionar of Patents

